On 2020-04-01 17:00, Luis Chamberlain wrote:
> Commit dc9edc44de6c ("block: Fix a blk_exit_rl() regression") moved
> the blk_release_queue() into a workqueue after a splat floated around
> with some work here which could sleep in blk_exit_rl().
>
> On recent commit db6d9952356 ("block: remove request_list code") though
> Jens Axboe removed this code, now merged since v5.0. We no longer have
> to defer this work.
>
> By doing this we also avoid failing to detach / attach a block
> device with a BLKTRACESETUP. This issue can be reproduced with
> break-blktrace [0] using:
>
> break-blktrace -c 10 -d -s
>
> The kernel does not crash without this commit, it just fails to
> create the block device because the prior block device removal
> deferred work is pending. After this commit we can use the above
> flaky use of blktrace without an issue.
>
> [0] https://github.com/mcgrof/break-blktrace
>
> Cc: Bart Van Assche <bvanassche@xxxxxxx>
> Cc: Omar Sandoval <osandov@xxxxxx>
> Cc: Hannes Reinecke <hare@xxxxxxxx>
> Cc: Nicolai Stange <nstange@xxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxxxx>
> Suggested-by: Nicolai Stange <nstange@xxxxxxx>
> Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> ---
> block/blk-sysfs.c | 18 +++++-------------
> 1 file changed, 5 insertions(+), 13 deletions(-)
>
> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> index 20f20b0fa0b9..f159b40899ee 100644
> --- a/block/blk-sysfs.c
> +++ b/block/blk-sysfs.c
> @@ -862,8 +862,8 @@ static void blk_exit_queue(struct request_queue *q)
>
>
> /**
> - * __blk_release_queue - release a request queue
> - * @work: pointer to the release_work member of the request queue to be released
> + * blk_release_queue - release a request queue
> + * @kojb: pointer to the kobj representing the request queue
> *
> * Description:
> * This function is called when a block device is being unregistered. The
> @@ -873,9 +873,10 @@ static void blk_exit_queue(struct request_queue *q)
> * of the request queue reaches zero, blk_release_queue is called to release
> * all allocated resources of the request queue.
> */
> -static void __blk_release_queue(struct work_struct *work)
> +static void blk_release_queue(struct kobject *kobj)
> {
> - struct request_queue *q = container_of(work, typeof(*q), release_work);
> + struct request_queue *q =
> + container_of(kobj, struct request_queue, kobj);
>
> if (test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags))
> blk_stat_remove_callback(q, q->poll_cb);
> @@ -905,15 +906,6 @@ static void __blk_release_queue(struct work_struct *work)
> call_rcu(&q->rcu_head, blk_free_queue_rcu);
> }
>
> -static void blk_release_queue(struct kobject *kobj)
> -{
> - struct request_queue *q =
> - container_of(kobj, struct request_queue, kobj);
> -
> - INIT_WORK(&q->release_work, __blk_release_queue);
> - schedule_work(&q->release_work);
> -}
> -
> static const struct sysfs_ops queue_sysfs_ops = {
> .show = queue_attr_show,
> .store = queue_attr_store,
The description of this patch mentions a single blk_release_queue() call
that happened in the past from a context from which sleeping is not
allowed and from which sleeping is allowed today. Have all other
blk_release_queue() / blk_put_queue() calls been verified to see whether
none of these happens from a context from which sleeping is not allowed?
Thanks,
Bart.
